The controllers are Kelly Control PM48501B with the joystick input option.   They are nominally 4-quadrant drives but they have a serious weakness as a 4-quadrant drive due to a deadband around zero speed.

I do not recommend these controllers for a boat.  In fact we are yet to find a suitable 4-quadrant PMDC controller.  The Kelly unit suffers from a lock-out condition whereby it locks-out if the motor is being driven forward by flow past it and the joystick is reversed.  It does not become active again until the prop stops rotating.  It has taken a long while to understand this problem.  Kelly now say the controller was designed for traction application where there is a mechanical brake that can stop the rotation.  They even tried firmware changes to correct the problem but to no avail.  

Once we knew the exact problem we have learnt to move within the marina at low speed; slow enough that it will not drive the props as turbines.  At low speed, when the joystick is centred the prop stops turning.  That ensure the units are always in control and reverse smoothly.

The maximum rpm at the props on the 50V batteries is close to 700rpm.  Motors do 2100rpm or so depending on load and the gearbox ratio is 1:3.3.

The controllers have a continuous rating of 200A.  The stated rating of 500A is meaningless for a boat as it is the break out  current the controller can produce operating against a brake at zero rpm.  I guess it is intended to give reliable hill starting by engaging forward drive against a mechanical brake then release the brake.  The high peak current at rest ensures it moves forward rather than rolling backward.

It should be noted that Kelly advertise the controller as suitable for marine use and are quite happy to contemplate dropping the anchor to arrest the speed if you really need to come to a halt when being driven by the wind for example and at risk of ramming something.   

The ME1003 motors have worked well to date.  These motors have brushes that have a nominated life of 4000hrs - that is a long time as a sailing auxiliary.  Under normal operation in and out of the marina  the motors are running at about 80A with 30V on the terminals.  Hence battery current is 50A.  

Under bollard pull test conditions the motors are torque limited by the 200A current limit.  Motor voltage gets to 33V so input power is 6.6kW and thrust was measured at 1300N on each unit.  At full throttle in calm conditions the motors operate just below the 200A current limit with full motor voltage around 49V - depending on the state of battery charge to get to 8.5kts.  Each unit has its own battery.  The first battery was selected on the basis of 1 hour use at 2.5kW so is 60Ah.  After initial trials with this battery and a single test drive unit the owner decided it would be good to go for a larger battery for the second unit so he selected 100Ah cells.  We operate both batteries at the 2 hour rate to give a combined 4kW - 2.5kW plus 1.5kW.  That gives somewhere between 4 and 6kts depending on the cleanliness of the hull and sea conditions.

It is possible to buy brushless motors with 4-quadrant controllers but none of the current crop have the efficiency or torque capability of the ME1003 motor.  Another option is induction motors but the costs skyrocket with these to get the same torque as the ME1003.  The original testing was done with a single ME3001 brushless motor which has embedded speed feedback so was a true 4-quadrant drive with no issue reversing when running forward. However its rated power is half the ME1003.

If you are considering controllers the key items are the continuous current rating and ability to reverse while the prop is being driven forward.  The attraction of the 4-quadrant drive is the electronic reversal but if it can only reverse when the prop has stopped it presents issues.  A lower cost and possibly better option would be contactor reversal.  From a drive perspective the bollard pull at rated torque/current and efficiency at nominated cruising speed are the main considerations.  

I am happy to help in critiquing options you may consider.  There are a few electric drives on the market now.  

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